# SerwerSMS, free trial, POST /phones/nat: Phone validation API

> Functionality allows you to monitor the availability of the number for 72 hours from the time of order.

SerwerSMS's phone validation API on its Free trial plan. It costs $0.00 per 1,000 phones. It returns 2 of the 9 key fields we check: Number, Validity.
We haven't run SerwerSMS through [our phone validation API benchmark](https://datacircle.dev/best-phone-validation-api.txt) yet.
This plan is free. We rank 888 plans for phone validation APIs by price. Half the plans cost $3.376 per 1,000 phones or less.
[Botoi's $199 monthly plan](https://datacircle.dev/validate-phone-apis/botoi/199-monthly/llms.txt) is the cheapest paid plan per 1,000 phones: as little as $0.0066. Botoi's $199 monthly plan covers up to 1,000,000 phones a day.
[Data247](https://datacircle.dev/validate-phone-apis/data247/12-pack-membership-get-v3-0-verify247-phone/llms.txt), [Foxentry](https://datacircle.dev/validate-phone-apis/foxentry/top-up-pay-as-you-go-post-phone-validate-validate-phone-number-extended/llms.txt) and [HLR Lookups](https://datacircle.dev/validate-phone-apis/hlr-lookups/top-up-1-1m-post-hlr-lookup/llms.txt) are the best phone validation API providers in the Datacircle benchmark.

- This page: https://datacircle.dev/validate-phone-apis/serwersms/free-trial-post-phones-nat
- [Phone validation API: 40+ providers compared](https://datacircle.dev/best-phone-validation-api.txt)
- Get it: https://en.serwersms.pl/pricing?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=phone-validation-api-pricing
- Request: `POST https://api2.serwersms.pl/phones/nat`
- API key: with the plan, on https://en.serwersms.pl/pricing?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=phone-validation-api-pricing
- Its API docs: https://dev.serwersms.pl/https-api-v2/nat-sprawdzanie-dostepnosci-numeru?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=phone-validation-api-pricing
- Sold by: SerwerSMS (https://www.serwersms.pl?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=phone-validation-api-pricing)
- Checked: 2026-11-04

## In the answer

- Completeness: 22%
- Number: ✓
- Validity: ✓

## Price

- $ per 1,000 phones: $0.00
- Billing: free

## Aggregators

- Aggregators: none

## Charges

- Also pays for: Sending SMS messages with the same content: 100 free messages

## Not found

- $ per 1,000: $0.00

## In their words

- Their pitch: Functionality allows you to monitor the availability of the number for 72 hours from the time of order.

## Data

- Countries: Poland
- What it checks: numbering plan, line in service
- Keep data: no limit
- Use data: Subscriber shall not be entitled irrespective of the technical means used to enable third parties to use Serwer SMS or to use Serwer SMS for third parties needs in any other way than described in the paragraph 2. [...] It is forbidden to share account to third parties, unless the Account is used by an authorized employee or associate of the Subscriber.

## Plan

- Pay: $0
- Expires: 14 days

## Speed

- Answer: by polling or webhook

## The call

- You send: phone. Optional: url
- Method: POST
- Path: /phones/nat

## About the plan

- Plan: Free trial
- Who can get it: entrepreneurs: its terms define a Subscriber as an entrepreneur

## The 3 fields the plan's answer can hold

phone number, status, check completed date

## SerwerSMS's plans (7)

- [SerwerSMS, free trial, POST /phones/nat](https://datacircle.dev/validate-phone-apis/serwersms/free-trial-post-phones-nat/llms.txt): $0.00 per 1,000, 22% complete
- [SerwerSMS, top-up from PLN 50, Prepaid, POST /phones/nat](https://datacircle.dev/validate-phone-apis/serwersms/top-up-from-pln-50-prepaid-post-phones-nat/llms.txt): $23.176 per 1,000, 22% complete
- [SerwerSMS, PLN 49 monthly, Lite, POST /phones/nat](https://datacircle.dev/validate-phone-apis/serwersms/pln-49-monthly-lite-post-phones-nat/llms.txt): $23.176 per 1,000, 22% complete
- [SerwerSMS, PLN 99 monthly, Standard, POST /phones/nat](https://datacircle.dev/validate-phone-apis/serwersms/pln-99-monthly-standard-post-phones-nat/llms.txt): $23.176 per 1,000, 22% complete
- [SerwerSMS, PLN 199 monthly, Growth, POST /phones/nat](https://datacircle.dev/validate-phone-apis/serwersms/pln-199-monthly-growth-post-phones-nat/llms.txt): $23.176 per 1,000, 22% complete
- [SerwerSMS, PLN 299 monthly, Pro, POST /phones/nat](https://datacircle.dev/validate-phone-apis/serwersms/pln-299-monthly-pro-post-phones-nat/llms.txt): $23.176 per 1,000, 22% complete
- [SerwerSMS, contact us, Individual package, POST /phones/nat](https://datacircle.dev/validate-phone-apis/serwersms/contact-us-individual-package-post-phones-nat/llms.txt): 22% complete

## SerwerSMS's calls (3)

- `POST /phones/check`: [SerwerSMS, free trial, POST /phones/check](https://datacircle.dev/validate-phone-apis/serwersms/free-trial-post-phones-check/llms.txt)
- `POST /phones/lookup`: [SerwerSMS, free trial, POST /phones/lookup](https://datacircle.dev/validate-phone-apis/serwersms/free-trial-post-phones-lookup/llms.txt)
- `POST /phones/nat`: [SerwerSMS, free trial, POST /phones/nat](https://datacircle.dev/validate-phone-apis/serwersms/free-trial-post-phones-nat/llms.txt)

## SerwerSMS's APIs (1)

- [SerwerSMS: phone validation API pricing, 7 plans, POST /phones/nat](https://datacircle.dev/validate-phone-apis/serwersms/free-trial-post-phones-nat/llms.txt)

## SerwerSMS: phone validation API alternatives

- [BigDataCorp, pay as you go, 1 - 10.000](https://datacircle.dev/validate-phone-apis/bigdatacorp/pay-as-you-go-1-10-000/llms.txt): $21.641 per 1,000, 44% complete
- [Kendo, $164 yearly](https://datacircle.dev/validate-phone-apis/kendo/164-yearly/llms.txt): $22.778 per 1,000, 22% complete, stored
- [HLR Lookup, £43 pack, 10,000 lookups, POST /apiv2/hlr, Full HLR lookup, full](https://datacircle.dev/validate-phone-apis/hlr-lookup/43-pack-10000-lookups-post-apiv2-hlr-full-hlr-lookup-full/llms.txt): $22.936 per 1,000, 89% complete, live
- [MTS Exolve, top-up, Базовый: до 50 000 запросов в месяц](https://datacircle.dev/validate-phone-apis/mts-exolve/top-up-50-000/llms.txt): $23.281 per 1,000, 11% complete, live
- [Postcoder, £296 monthly](https://datacircle.dev/validate-phone-apis/postcoder/296-monthly/llms.txt): $23.683 per 1,000, 56% complete, live

## Sources

From each provider's own pricing page and docs, and from what providers tell us. We read this row from these pages on 2026-11-04.

- https://dev.serwersms.pl/https-api-v2?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=phone-validation-api-pricing
- https://dev.serwersms.pl/https-api-v2/autoryzacja?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=phone-validation-api-pricing
- https://dev.serwersms.pl/https-api-v2/nat-sprawdzanie-dostepnosci-numeru?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=phone-validation-api-pricing
- https://docs.serwersms.pl/SerwerSMS_term_of_use.pdf?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=phone-validation-api-pricing
- https://en.serwersms.pl/pricing?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=phone-validation-api-pricing
- https://en.serwersms.pl/services/checking-numbers?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=phone-validation-api-pricing
- https://serwersms.pl/cennik/cennik-pre-paid?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=phone-validation-api-pricing